Catalyst Comprising Active Particles Physically Pinned to the Support

Abstract

Catalyst comprising: a) a catalytic ceramic support comprising an arrangement of crystallites of the same size, same isodiametric morphology and same chemical composition or substantially of the same size, same isodiametric morphology and same chemical composition in which each crystallite is in point contact or virtually point contact with crystallites that surround it, and b) at least one active phase comprising metallic particles mechanically anchored into said catalytic support so that the coalescence and the mobility of each particle are limited to a volume corresponding to that of a crystallite of said catalytic ceramic support.

1 - 10 . (canceled) 
     
     
         11 . A catalyst comprising:
 a) a ceramic catalyst support comprising an arrangement of crystallites of the same size, same isodiametric morphology, and same chemical composition or substantially the same size, same isodiametric morphology, and same chemical composition, in which each crystallite is in point or quasi-point contact with its surrounding crystallites, and   b) at least one active phase comprising metal particles anchored mechanically in said catalyst support such that the coalescence and mobility of each particle are limited to a maximum volume corresponding to that of one crystallite of said ceramic catalyst support.   
     
     
         12 . The catalyst of  claim 11 , wherein said arrangement is in spinel phase. 
     
     
         13 . The catalyst of  claim 11 , wherein the metal particles are selected from rhodium, platinum, palladium and/or nickel. 
     
     
         14 . The catalyst of  claim 11 , wherein the crystallites have an average equivalent diameter of between 5 and 15 nm, preferably between 11 and 14 nm, and the metal particles have an average equivalent diameter of between 2 and 10 nm, preferably less than 5 nm. 
     
     
         15 . The catalyst of  claim 11 , wherein the arrangement of crystallites is a face-centered cubic or close-packed hexagonal stack in which each crystallite is in point or quasi-point contact with not more than 12 other crystallites in a three-dimensional space. 
     
     
         16 . The process for preparing a catalyst of  claim 11 , comprising the following steps:
 a) preparing a ceramic catalyst support comprising an arrangement of crystallites of the same size, same morphology, and same chemical composition or substantially the same size, same morphology, and same chemical composition, in which each crystallite is in point or quasi-point contact with its surrounding crystallites;   b) impregnating the ceramic catalyst support with a precursor solution of the metallic active phase;   c) calcining the impregnated catalyst in air at a temperature of between 450° C. and 1000° C., preferably at a temperature of between 450° C. and 700° C., more preferably still at a temperature of 500° C., to give an oxidized active phase coated on the surface of the catalyst support; and   d) reducing the oxidized active phase at between 300° C. and 1000° C., preferably at a temperature of between 300° C. and 600° C., more preferably still at a temperature of 300° C.   
     
     
         17 . The preparation process of  claim 16 , wherein impregnation step b) is carried out under vacuum for a duration of between 5 and 60 minutes. 
     
     
         18 . The process of  claim 16 , wherein step b) the solution of active phase is a rhodium nitrate (Rh(NO 3 ) 3 .2H 2 O) solution or a nickel nitrate (Ni(NO 3 ) 2 .6H 2 O) solution. 
     
     
         19 . The process of  claim 16 , wherein said process, after step d), includes a step e) of hydrothermal aging of the catalyst. 
     
     
         20 . The use of the catalyst of  claim 11  for the steam reforming of methane.